Glyphosate is well known as a highly effective and commercially important herbicide useful for combating the presence of a wide variety of unwanted vegetation, including agricultural weeds. Glyphosate is conventionally applied as a formulated product dissolved in water to the foliage of annual and perennial grasses and broadleaf plants and the like, is taken up over a period of time into the leaves, and thereafter translocates throughout the plant.
Under most application conditions, the herbicidal efficacy of glyphosate can be significantly enhanced by including one or more surfactants in the composition to be applied. It is believed that such surfactants act partly by facilitating the penetration of glyphosate, a relatively hydrophilic compound, through the rather hydrophobic cuticle which normally covers the external above-ground surfaces of higher plants.
In some glyphosate formulations, certain glyphosate salts are preferred. For example, in some applications potassium glyphosate is preferred because it can be more highly loaded and is of lesser cost than many other glyphosate salts. However, potassium glyphosate is not highly compatible with some surfactants used in the art, such as tallowamines having from about 8 to about 25 ethoxy units.
It is known that potassium glyphosate shows good compatibility with etheramine alkoxylate surfactants of the formula:
wherein R is C8 to C18, z is a number from 1 to 5 and m and n are average numbers such that m+n is in the range of from 2 to about 8. Commercial potassium glyphosate formulations typically contain up to about 135 g/L of such etheramines. Etheramine alkoxylate surfactants generally provide high herbicidal efficacy on weeds when formulated in compositions at concentrations in excess of about 120 grams per liter (“g/L”), but also may cause crop damage and eye irritation at that concentration. In particular, when formulated in excess of about 120 g/L, etheramines are generally placed in toxicity category II when tested according to the standard procedure prescribed in US Environmental Protection Agency (EPA) Publication 540/9-82-025, November 1982, entitled Pesticidal Assessment Guidelines, Subdivision F, Hazard Evaluation: Human and Domestic Animals, thereby indicating moderate eye irritation. In contrast, at low concentrations (such as about 65 g/L as described, for example, in U.S. Pat. No. 5,750,468 to Wright) etheramine alkoxylate surfactants are placed in toxicity category III indicating low irritancy to eyes. However, at such low surfactant concentrations herbicidal efficacy is not enhanced to the extent that it is in potassium glyphosate compositions containing significantly greater proportions of etheramine.
It is further known that glyphosate formulations containing etheramine alkoxylate surfactants can cause relatively greater crop injury to certain glyphosate tolerant plants such as Roundup Ready® corn, soybeans, canola or cotton as compared glyphosate formulations containing other surfactants known in the art.
A need exists for high efficacy etheramine-based herbicide compositions that are compatible with herbicides and salts thereof including the potassium salt, that cause little or no crop damage, and that have low eye irritancy and low toxicity.